Process for drawing and continuously heat-setting synthetic filaments

ABSTRACT

AN IMPROVED PROCESS FOR DRAWING AND CONTINOUSLY HEAT-SETTING FILAMENTS OF SYNTHETIC, MELT-SPINNABLE POLYMERS INVOLVES INCREASING THE COHERENCY OF THE FILAMENT BUNDLE DURING SUCH PROCESSING BY FALSE-TWISTING IN THE DRAWING ZONE.

v J. D. GUTMANN, JR 3,555,808

PROCESS FOR DR NG AND CONTINUOUSLY HEAT-SETTING j NTHETIC FILAMENTS Filed 001;. 9. 1968 INVENTOR ATTORNEY JOSEPH D. GUTMANN, JR

United States Patent IL. Cl. 57-157 7 Claims ABSTRACT OF THE DISCLOSURE An improved process for drawing and continuously heat-setting filaments of synthetic, melt-spinnable polymers involves increasing the coherency of the filament bundle during such processing by false-twisting in the drawing zone.

DESCRIPTION OF THE INVENTION Individual filament separation on machine processing rolls can lead to excessive filament damage at contact points on rolls and guide pins or to entanglement with filaments from neighboring filament bundles being processed on the same equipment. Filament separation is generally reduced through the conventional processing techniques that include application of an oily lubricating finish to the filaments prior to the first process roll. For subsequent processing requirements such as in a textile mill, it generally is desirable to maintain the level of this spinning finish as low as possible.

Separation or splaying of filaments is accentuated during processing at high speeds, particularly with filaments having relatively low hydrodynamic frictional running properties. An example of such filaments are those having delusterant particles dispersed therein which particles protrude above the normally smooth filament surface. Such filaments exhibit a reduced tendency to splaying only when coated with an abnormally high level of finish. However, the presence of such high level of finish causes high and nonuniform running tensions during handling in a textile mill or interferes with textile sizing operations. In some instances acceptable processing can be obtained temporarily by applying more dilute finish compositions; however, when such filaments come into contact with heated surfaces the water is flashed off by evaporation and they are again dependent upon the residual oil finish for subsequent processing.

In accordance with this invention, filaments comprised of a synthetic, melt-spinnable polymer are drawn to produce molecular orientation, and forwarded by means of multiple wraps around a pair of coacting, heated draw rolls. During draw the filament bundle is subjected to a pneumatic false-twisting operation to impart cohcrency to the bundle. The filament bundle is forwarded and heat-set by means of multiple wraps around said pair of heated draw rolls. The drawn, heat-set yarn should have an average twist (determined as described below) of at least about 0.05 twist per inch. The twist will normally not exceed about 0.3 twist per inch due to the tension of drawing.

The yarn forwarded by the heated draw rolls preferably contains less than 1.5% by Weight of finish. The heated draw rolls will ordinarily be maintained at a temperature of 100 to 200 C. The tension on the yarn at the point of false-twisting can be from about 0.5 to 2.0 grams per denier (g.p.d.). At surface speeds of the heated draw rolls from about 1500 to 3500 yards per minute, the direction of false-twisting should preferably be alternated at a frequency of from 1 to 30 cycles/ second.

The present invention is of particular value in the 3,555,808 Patented Jan. 19, 1971 processing of synthetic polycarbonamide yarns which require heat-setting after drawing, e.g., polycarbonamides from bis-(4-aminocyclohexyl)methane and linear, aliphatic dicarboxylic acids containing from 9 to 16 carbon atoms, and which contain at least 0.5% by weight of hexagonal platelets of aluminum silicate having kaolinite crystal structure which platelets have an average particle size of 0.2 to 2.0 microns and are substantially free of all particles larger than about 5 microns. Such yarns and others of relatively low hydrodynamic frictional running properties are disclosed in US. 3,314,919 and 3,397,171. Other synthetic polymeric yarns containing the aluminum silicate or other surface roughening agents would also benefit from the instant process.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings, FIG. 1 is a schematic illustration of a process installation on which multiple filament bundles (yarns) can be processed by this invention. FIG. 2 is an exploded view of a suitable jet device for false-twisting of multiple filament bundles. FIG. 3 is an illustration of another alternate-twisting jet device which is suitable for use in the process.

The process installation chosen for purposes of illustration in FIG. 1 includes a spinning block and spinnerets 10 from which groups of filaments 11 are extruded and separated into separate bundles and quenched in quenching zones 12. The filament bundles 11 are converged and a lubricating finish is applied by means of finish rolls 13. The yarns then pass to feed rolls 15. The separate filament bundles (yarns) are simultaneously subjected to drawing in two stages by multiple wraps around three sets of motor-driven rolls, each successive set of rolls having a higher surface speed than the previous set. The roll sets are the feed rolls 15, first stage draw rolls 16 and heated, second stage draw rolls 19 which are enclosed in a heated box 18. In the case of single stage drawing, rolls 16 would be omitted. Prior to entering box 18, each of the filament bundles is subjected separately to the action of a pneumatic, torque jet device 17 located between the first and second stage draw rolls. Guide pins 25 serve to align the bundles 11 leaving jet device 17 and prevent the splaying action of the jet on the filaments from being transmitted along the yarn onto the second stage draw rolls. Optionally, similar guide pins may be located between jet device 17 and roll 16 if needed to prevent entanglement of filaments between bundles prior to the jet device as the result of splaying action within the jet device 17 when the bundles are closely spaced. Air flow in the jet device introduces a low amount of alternating twist to the stretched filaments and rearranges filament bundle geometry so that filament separation does not occur on the heated second stage draw roll 19 surfaces. The yarns leaving rolls 19, pass around a tension letdown roll 20 and a puller roll 21, which reduce yarn tension in a controlled manner and deliver the yarns to a second finish applicator roll 22 where a second film of finish is supplied when needed, as for protection during processing in a textile mill. Subsequent to the second finish application the yarns are wound separately in package form on a windup apparatus 24. There may also be an interlacing jet device or means for additional twisting located below the secondary finish roll prior to packaging to impart additional filament bundle cohesion when desired.

FIG. 2 shows an exploded view of a jet device 17 of FIG. 1, consisting of three pieces, top piece 27, center piece 28 and bottom piece 29. Each piece contains stringup slots 30 and yarn channels 31. In center piece 28, compressed air is fed alternately from two separate air passages (not shown) through manifolds 32 (top and bottom respectively) to air channels 33 and then to yarn channels 31. Air channels 33 on the top and bottom of center piece 28, feed in rotationally opposite directions to yarn channels 31 such that alternate feeding of air between the top and bottom manifolds exerts alternate rotation to the air flow in yarn channels 31.

Suitable means such as rotating valve asemblies, etc., may be employed as described in U.S. Pat. 3,022,566, shown for example in FIG. a therein to alternate the air supply to the two separate passages leading to the top and bottom manifolds of center piece 28.

FIGS. 3A and 3B show an alternate jet device design. Air manifolding in center piece 28 is similar to that in FIG. 2 except that the manifold lies between the two rows of yarn channels 31.

DETAILED DESCRIPTION In this invention, the jet devices are employed to alternately twist the continuously moving yarn in opposite directions. Suitable devices for this purpose are disclosed in U.S. Pat. No. 3,079,745. Because of the relatively high tension on the filaments in the drawing zone during the twisting operation, the twisting efficiency is greatly reduced from that of prior art usage. Consequently, characterization of the treated yarns with respect to twist and coherency is much more difliicut than for yarns processed under lower tension conditions as described in the prior art, for example in U.S. Pat. No. 3,022,566. In spite of the higher tension, it has been found that the yarns can be twisted sufficiently so that the yarn retains its coherency throughout processing on the subsequent roll surfaces. Because of the low twist or filament entanglement under the conditions oft he process, yarns processed by this invention normally will not have sutficient coherency to eliminate the need for additional twisting or interlacing by knokn processes in subsequent textile processing operations. For example, yarn processed by this invention ordinarily will retain an average twist level of less than about 0.3 twist/inch (t.p.i.). Normally, an average false twist of at least about 0.5 t.p.i. is desired for acceptable processing of so-called twist-free yarns in normal textile processing operations. Such twisting processes are performed as described for example in US. Pat. No. 3,116,588 at relatively low yarn tension.

Operation of the jet device at oscillation frequencies from about 1 to 30 cycles/ second and air pressures from 5 to 100 p.s.i.g. have been found suitable for alternate twisting of the yarn. Under these conditions it has been found that finish levels on the processed yarns can be as low as from about 0.1 to 0.6% by yarn weight without significant separation of the filaments on the heated rolls. Air at room temperature is the preferred fluid medium for operating the jet devices.

EXAMPLE I Trilobal filaments of a synthetic polyamide and a copolymer thereof are melt cospun through separate holes in a single spinneret and drawn on a process position of the type shown in FIG. 1. Half of the filaments in the yarn bundle are of the homopolymer and half the copolymer. The homopolymer is a polymer prepared from bis(4-aminocyclohexyl) methane and dodecanedioic acid (1,10-decane dicarboxylic acid) and the copolymer thereof has by weight of the polymer replaced with polymer units from isophthalic acid and the same diamine. The diamine contains 70% by weight of the trans-trans isomer. The 36-filament yarn has a drawn denier of about 60. Both types of polymers contain uniformly dispersed therein about 2% by weight of kaolinite having particles sizes within the range of about 0.3 to 3.0 microns as a delusterant and filament surface modifier.

The yarn is drawn in two stages with a draw ratio of 1.14 between the feed rolls (3 wraps) and the first stage draw rolls (3 wraps) and a draw ratio of 1.l4 between the first stage draw rolls and the heated, second stage draw rolls (7.5 wraps). The second stage draw rolls have a diameter of 1.64 inches and are positioned at a center-to-center distance of about 10 inches apart in a slightly skewed position. The latter are maintained at a temperature of 170 C. with heated air and are enclosed in a heated box of the type described for example in U.S. Pat. 3,161,484. The heated rolls are op erated at a surface speed of 3000 yards/ minute. The yarn passes through a pneumatic, alternating twist, torque jet device positioned between a first and second stage draw rolls. The jet is powered by air at room temperature operating through an assembly which alternates flow of air in the jet at the desired frequency.

The jet device employed is that shown in exploded view in FIG. 2. The yarn channels 31 of the three metal pieces 27, 28, and 29 are .125 in diameter, the total length along a yarn channel being two inches. The yarn channels are arranged at the corners of an equilateral triangle, the length of one side being .374 inch and each yarn channel has a thin slotted entrance of string-up slot 30, 0.010 inch wide suitable for admitting a moving yarn. In addition to the above-mentioned features, part 28 has machine into it identical air manifolds 32 on top and bottom which are situated equidistant from the three yarn channels and are .100 inch deep by .200 inch diameter. Curved air channels 33 join the manifolds 32 with yarn slots 31 such that channels 33 enter yarn channels 31 tangentially at the string-up slots 30'. Air channels 33 on the under side of part 28 are identical to those shown but are of opposite curvature when viewed from one side of the part. Air channels 33 are .035 inch wide by .100 inch deep. Air is admitted to manifolds 32 by air channels having their entrances situated at the back of the assembly and threaded to provide attachment to suitable air piping, For this example only one yarn channel is used, the remaining two channels operating but without yarn.

Yarn tension between the first and second stage draw rolls is about 110 grams or about 1.83 grams per denier (g.p.d.). Prior to drawing, a lubricating finish emulsified in a water base (1.5% finish by weight of the emulsion) is applied to the yarn to give a finish level on yarn (exelusive of water which flashes otf when the yarn is heated by the second stage draw rolls) of about 0.25-0.35 by weight of yarn. With the jet operating at about 10 cycles/ second with an air pressure of 35-37 lbs/in. yarn packages from continuous one hour dotf cycles are obtained. When the jet device is shut off under these operating conditions, the process never runs longer than 40 seconds because of severe spreading of the filaments of the heated rolls resulting in accumulation of broken filaments on guide pins located at the exit of the heated box.

EXAMPLE II Example I is repeated except that four yarn bundles are processed. Yarns are prepared over a range of draw ratio conditions of 1.141.17 in both the first and second stage drawing zones with the heated second stage draw rolls correspondingly operating at a speed of 2600-3000 y.p.m. Yarn tension between the first and second stage draw rolls is within the range of -110 grams or about 1.51.85 g.p.d. Finish is applied (LS-2.0% finish by weight of emulsion in water) to give a final finish content on yarn (exclusive of water) of about 0.5- 0.6% by weight of yarn.

A jet device of the type shown in FIG. 3 is positioned approximately midway between the first and second stage draw rolls. It is of three-piece construction like the one shown in FIG. 2. The length when assembled is 2 inches. Center part 28 is 0.25 inch thickand contains yarn channels 31 which are 0.125 inch diameter. String-up slots 30 permit access of the running threadline to yarn channels 31 and are 0.010 inch wide. Identical manifolds 32 recessed in top and bottom of part 28 are situated midway between channels 31 and are 0.100 inch deep and 0.2 inch wide. Curved air channels 33 are designed such that their sides of largest radii are tangent to channels 31 at string-up slots 30 and are 0.035 inch wide and 0.100 inch deep. Channels 33 are also designed such that all those belonging to one of the two manifolds 32 produce air flow patterns in channels 31 having the same direction of rotation while those belonging to opposite manifold produce air flow patterns in opposite directions when viewed from one end of channels 31. The width of the device is 0.81 inch and channels 31 have their centers situated 0.189 inch from the edge. The distance between channels 31 on one side is 0.356 inch; the distance between neighboring channels 31 on opposite sides is 0.416 inch. Two separate air passages are provided at one end of the assembly to connect air from a source to the manifolds 32.

In operation, air is pulsed alternately to manifolds 32 at a desired frequency. This pulse air flow is then led into yarn channels 31 by air channels 31 from manifolds 32. The effect of air entering channels 31 is to impart an alternating clockwise/ counterclockwise circular motion to the filament bundle producing alternating false twist in the moving yarn.

With the jet device operating at 8 cycles/ second at an air pressure of 40-45 lbs./in. gauge yarn packages from continuous one-hour dotf cycles are obtained.

When the jet device is shut off under these operating conditions there appear on the second stage draw ro lls continuous or intermittent wide bands of filaments, where before there existed coherent filament bundles. The result of this splayed condition is a rapid accumulation of broken filaments on all subsequent yarn guides (an indication of poor yarn mechanical quality) eventually resulting in a complete yarn break prior to the full bobbin dolf time of 60 minutes. With the jet device operating, there are no broken filaments evident on the guides during any one 60-minute dotf.

The packaged yarn with the jet device in operation as described has an average twist (disregarding direction of twist) of less than 0.2 t.p.i. (0.08 t./cm.) measured as described in Example III.

The drawn yarn has a hydodynamic friction of about half that of yarns of the same composition prepared in a similar manner but not containing the kaolinite. Reduced interfilament friction caused by surface roughening from protusion of the kaolinite particles in the filaments is a major factor in their poor processability on roll surfaces as shown above.

EXAMPLE HI This example describes a test run in an attempt to determine the efiect of a pneumatic jet device of the type shown in Example II on yarn filament geometry under processing conditions as described in Example II.

Filaments are spun and draw in a manner similar to that described in Example II except that the pneumatic jet device is moved from its position between the draw rolls to a position immediately before the yarn wind-up apparatus, and winding tension (normally about grams) is increased to simulate the drawing tension (90-110 grams) with a 60-denier yarn. However, due to a technical problem of winding at high tension the closest approach to actual yarn processing tension is 50 grams. A series of yarn samples are obtained and analyzed to determine the filament bundle geometry going onto the hot, second stage draw rolls from the jet device. It is determined that false twist of the filament bundle is in phase with oscillator frequency and that twist amplitude is related to the air pressure. The average twist at the preferred process settings of 8 cycles/second and less than or equal to 50 p.s.i.g. is less than or equal to about 0.3 t.p.i. Results of these measurements are shown in Table I.

P.s.i.g./cycles per second.

In all cases the yarn twist obtained is considerably less than 0.5 t.p.i. (twist per inch) but is sufficient to provide acceptable filament coherency.

The average twist is determined conventionally by measuring twist at consecutive intervals along the yarn and calculating the average twist for the total number of measurements made (both S and Z twist). The measurements are made at consecutive intervals of 12 inches and the average values reported are from a total of 55-60 measurements,

Many different kinds of pneumatic twisting jet devices, intermittent unidirectional and, preferably, alternating twist, may be employed in carrying out the process of this invention. In addition to those described herein suitable jet devices are also described in US. Pat. 3,022,566 and UJS. Pat. 3,079,745. Any suitable means as for example that shown in US. Pat. 3,022,566 may be used to control the operating frequency.

The process of this invention is particularly applicable in the processing of filaments having reduced surface friction, for example through the introduction of surface modifying agents which tend to roughen the filament surface and reduce the hydrodynamic friction thereof.

For any given process the preferred operating condition will depend upon obvious factors such as jet device design, yarn and filament denier, filament cross section, yarn tension and speed, etc., and can be readily determined by one skilled in the art for any given situation. The practice of this invention is of particular advantage in the drawing and heat-setting of continuous multifilament, synthetic yarns wherein low levels of finish on yarn are desired, either because of the need to apply another finish for specific subsequent textile processing operations, or 'where high levels of finish are not economical and the use thereof presents processing disadvantages. It may be practiced on any synthetic yarn which is drawn and processed as described herein. Although the process for the invention has been exemplified in use during the sec ond stageof a two-stage drawing operation (when the first stage draw rolls are feed rolls for the second stage drawing), the advantages are obtained in a single-stage draw, hot rolling annealing process as well.

What is claimed is:

1. A process comprising extruding groups of synthetic melt spun filaments containing a surface roughening agent, arranging said filaments in bundles, forwarding said bundles by means of a set of feed rolls, drawing the separate bundles simultaneously in a draw zone as they advance between the feed rolls and a set of heated draw rolls, false twistng each of the filament bundles separately as they advance through a draw zone immediately preceding the heated draw rolls under a tension from about 0.5 to 2.0 g.p.d., heat setting the yarns on the heated draw rolls and winding up the yarns separately in package form.

2. The process of claim '1 wherein the filament bundles forwarded to the heated draw rolls contain less than about 1.5% by weight of finish.

3. The process of claim 1 wherein each yarn leaving the heated draw rolls has an average twist of at least about 0.05 and less than about 0.3 twist per inch.

4. The process of claim 1 wherein the filament bundles proceed between the feed rolls and the heated draw rolls at a velocity of from about 1500 to 3000 yards per minute and the direction of false twisting is alternated at a frequency of from about 1 to 30 cycles/ second.

5. The process of claim 1 wherein the separate filament bundles leaving the feed rolls are drawn in two stages, the first draw taking place between the feed rolls and the first stage draw rolls, and the second draw and false twisting occurring between the first stage draw rolls and a set of heated second stage draw rolls.

6. The process of claim 1 wherein said filaments contain as a surface roughening agent, at least 0.5% by weight of hexagonal platelets of alumina silicate having kaolinite crystal structure, which platelets have an average particle size of 0.2 to 3.0 microns and are substantially free of all particles larger than about 5 microns.

7. The process of claim 6 wherein the synthetic filaments are polycarbonamides from bis(4-aminocyclohexyl) methane and linear, aliphatic dicarboxylic acids containing from 9 to 16 carbon atoms.

References Cited UNITED STATES PATENTS 10/ 1943 Hanson 57157X 5/1959 Kline et al. 57-157 9/1959 'Mayner 57157X 6/1961 Quittner 57-157 1/1962 Maier et al 57-157 2/1962 Daniels et al. 57--77.3X.

12/1962 Dahlstrom et al 57-157 10/1968 Tompkins 57'157X STANLEY N. GILREATH, Primary Examiner W. H. SOHROEDER, Assistant Examiner US. Cl. X.R. 

